[Regulation of inflammatory response based on interaction among AGEs, DAMPs, and/or cytokines]

Advanced Glycation End Products (AGEs) are produced through a non-enzymatic reaction between reducing sugar and biomolecules. These molecules are suggested to stimulate several receptors and activate inflammatory reactions. Because the accumulation of AGEs was found to be associated with hyperglycemia and/or aging, these molecules should be contributed to the pathogenesis of inflammatory diseases related to these conditions. Interestingly, possible receptors to engage AGEs are common to endogenous proinflammatory factors called damage-associated molecular pattern molecules (DAMPs). This raised the possibility that the action mechanism of AGEs and DAMPs is closely correlated. Previously, we found that AGEs interacted with high mobility group box-1 (HMGB1), a representative DAMP, and that this interaction activated the proinflammatory activity of HMGB1. These findings suggested that exacerbation of inflammation induced by HMGB1 was caused by the condition accumulating AGEs. In addition, AGEs were found to change the action of tumor necrosis factor-like weak inducer of apoptosis (TWEAK) through their direct interaction. TWEAK is called a multifunctional cytokine, and is suggested to regulate tumor necrosis factor-α (TNF-α) induced inflammatory reactions. We found that coexistence of AGEs and TWEAK inhibited this action of TWEAK, suggesting that accumulation of AGEs induces exacerbation of inflammation induced by TNF-α. Furthermore, we found ribosomal protein L9 (RPL9) as a novel AGE-binding protein. RPL9 inhibited HMGB1-induced inflammatory reaction, suggesting that RPL9 is the endogenous regulator for DAMPs. These findings suggested that there is a novel mechanism to regulate inflammatory reactions through the interaction among AGEs, DAMPs, and/or cytokines.